In recent years, the use of wireless mobile communication systems has become increasingly popular. For example, wireless mobile terminals now serve to help automate and expedite processes in retail, manufacturing, warehousing and other industries. In a retail environment, wireless mobile terminals may take the form of a wireless bar code reading device for use in tracking inventory and checking prices. In the warehousing industry, the same mobile terminals may be used to keep accurate accounting of incoming and outgoing shipments. In health care, transportation and other industries, the mobile terminals may take the form of wireless pen based computers to aid with on-site document control procedures, etc. In order to provide for real time communication, the mobile terminals often include a radio which allows them to communicate with a host computer connected to a LAN, for example.
LANs typically allow for connecting of devices operating in a building or specified site. Devices physically connected to the LAN may include desk top computers, printers and host computers. If the LAN also supports wireless mobile terminals such as those mentioned above, the LAN will also have connected thereto one or more access points (sometimes referred to as base stations). Each access point is coupled to the LAN and includes at least one radio through which wireless communication with the mobile terminals can occur.
Each access point can communicate with mobile terminals operating within the cell coverage area of the access point. The cell coverage area is the area in which the access point can reliably communicate with a mobile terminal. Once the mobile terminal roams outside of the cell coverage area of the access point, the mobile terminal can no longer communicate with the LAN through that particular access point. In order to provide cell coverage throughout an entire building or site, a LAN typically includes multiple access points strategically located throughout the building or site. Thus, the combined cell coverage of the access points is sufficient to cover the entire building or site. Mobile terminals may then roam from one area to another within the LAN.
As a mobile terminal roams throughout a LAN, it is important that an end to end session established between the mobile terminal and a device coupled to the backbone be maintained as the mobile terminals move from one cell to another cell. Known techniques for providing such seamless roaming from one access point to another access point within a given LAN are described in U.S. Pat. No. 5,276,680, for example.
However, recent trends have shown a desirability for mobile terminals to be able to roam not only within a given LAN, but also among different LANs and/or wide area networks (WANs). Although there are known techniques for allowing mobile terminals to roam seamlessly from one access point to another within a given LAN, this does not include the ability for mobile terminals to roam seamlessly from LAN to LAN, or LAN to WAN, for example. According to current technology, when a mobile terminal wishes to roam from one LAN to another the mobile terminal typically must disassociate itself from one LAN and reassociate itself with another LAN. This break in communication makes it difficult for information originating from the former LAN to be forwarded to the mobile terminal in the new LAN. Such difficulty adds overhead such as time and complexity associated with establishing a new connection.
Further, regardless of whether a mobile terminal roams to different LANs or WANs, information may also be lost if a connection (also referred to as a session) between the mobile terminal and some device on the LAN terminates for whatever reason. Such termination of a session may occur, for example, due to the mobile terminal not responding to communication from the device on the LAN due to the mobile terminal having roamed out of coverage area or because the mobile terminal is in a power savings mode.
In view of the aforementioned shortcomings with conventional techniques, it will be appreciated that there is a strong need in the art for a wireless mobile communication system which provides for seamless roaming among different networks. In particular, there is a strong need in the art for a system which provides for seamless roaming between different LANs each forming part of a WAN.